The present invention relates to a sputtering target-backing plate assembly used when titanium (Ti) is a sputtering target material, and in particular relates to a sputtering target-backing plate assembly capable of absorbing strain at an interface between the target and the backing plate in order to prevent deformation (displacement) during sputtering. The present invention also relates to a production method thereof.
In recent years, a sputtering target of titanium (Ti) has been needed for MRAM. A target is usually bonded to a backing plate and sputtering is performed at high power in order to increase production efficiency. Issues when performing this high power sputtering are hardness and cooling capacity of the backing plate itself, and the bonding strength between the backing plate and the target.
As conventional technologies, several ideas have been proposed for increasing bonding strength between a target and a backing plate. These are described briefly in the following. For example, there is a technology in which Ag or an Ag alloy is inserted as an insert material to perform solid phase diffusion for bonding a target material of Al or an Al alloy to a backing plate (see Patent Document 1).
There is another technology in which concentric unevenness is formed at a bonding surface between a sputtering target and a backing plate, and bonding is performed by the HIP, hot press, or solid phase diffusion bonding method while they remain fitted with each other (see Patent Document 2).
There is also a technology in which a target material having a melting point of 1000° C. or higher is bonded to a backing plate by solid phase diffusion via an insert material (Al, Cu, Ni and alloys thereof) having a melting point lower than that of the target (see Patent Document 3).
There is also a technology in which bonding is performed at low temperature via fine grains of copper placed between a sputtering target and a backing plate (see Patent Document 4).
Furthermore, there is a technology in which bonding is performed by explosion bonding or hot rolling via a spacer of Al or an Al alloy placed between a sputtering target and a backing plate (see Patent Document 5). Moreover, a sputtering device has been disclosed in which unevenness is provided at a cooling surface of a backing plate to increase its surface area (see Patent Document 6).
In addition, Patent Document 7 describes a technology in which diffusion bonding is performed via an insert material of an aluminum or aluminum alloy plate having a thickness of 0.8 mm or more for a tantalum or tungsten-copper alloy backing plate assembly.
Further, Patent Document 8 describes a technology in which diffusion bonding is performed via an insert material of an aluminum or aluminum alloy plate having a thickness of 0.8 mm or more for a diffusion bonded assembly of high-purity cobalt and a copper alloy backing plate.
Still further, Patent Document 9 describes a sputtering target in which backing plate material 4 having plural metal layers 2, 3, and target material 5 are bonded together by diffusion bonding or welding.
Yet further, Patent Document 10 describes that, when solid-phase diffusion bonding is performed to a target and a backing plate via an insert material, one or both sides are subject to a planarization process to give a roughness Ra 0.01 to 3.0 μm.
Even yet further, Patent Document 11 describes a bonding method in which when a target and a backing plate are bonded, elastomer resin having metal mesh therein is used.
Furthermore, Patent Document 12 describes that copper, aluminum or an alloy foil thereof is sandwiched between a target and a backing plate to perform sputtering.
These Patent Documents describe devised bonding methods for increasing the bonding strength between a sputtering target and a backing plate. However, neither a problem nor means for solving the problem has been disclosed at all, the problem being with regard to the amount of strain resulting from materials of the backing plate and the target, in particular, strain generation when using titanium as a target and a Cu—Cr alloy as a backing plate.
Patent Document 1: Japanese Patent Laid-Open No. H6-172993
Patent Document 2: Japanese Patent No. 4017198
Patent Document 3: Japanese Patent Laid-Open No. H6-108246
Patent Document 4: Japanese Patent Laid-Open No. S55-152109
Patent Document 5: Japanese Patent Laid-Open No. H4-131374
Patent Document 6: Japanese Patent Laid-Open No. H6-25839
Patent Document 7: Japanese Patent No. 3905301
Patent Document 8: Japanese Patent No. 3905295
Patent Document 9: Japanese Patent Laid-Open No. 2001-295040
Patent Document 10: Japanese Patent Laid-Open No. 2000-239838
Patent Document 11: Japanese Patent Laid-Open No. 2006-33603
Patent Document 12: Japanese Patent Laid-Open No. H11-189870